The majority of biochemical samples are complex mixtures. Separation and isolation of each component prior to analysis is often laborious and tedious. Therefore, considerable effort has been expended on the development and application of methodologies designed to separate and introduce each separated component of a mixture directly into a mass spectrometer. GC/MS, used for the separation and analysis of volatile and thermally stable substances is a relatively mature technique. LC/MS, which combines liquid chromatographic separation with MS analysis is still at a stage where several interfaces are in popular use and where the capabilities of the technique in its various manifestations have not been thoroughly explored. We are currently exploring the applicability of thermospray (TSP) as an LC-MS interface for biochemical problems. Several studies are being carried out concurrently including: 1) determination of glutathione and related ccnjugates (cysteine, N-acetylcystene) of exogenous chemicals; 2) analysis of the highly toxic senecionine alkaloids and their microsomal metabolites: 3) analysis of the herbicide metribuzine and its plant metabolites; 4) ANF (alpha- naphthoflavone) metabolites; and 5) the metabolic products of H.C. Blue No. 1 and H.C. H.C. Blue No. 2 (H.C. Blue No. 1 is a carcinogen previously used in hair dye.